This invention relates to a surface treatment technology for practicing etching, ashing, reforming, and formation of a thin film for a surface of a subject of treating whose surface is difficult to treat for the reason such that it is placed at a separated position, or it has a complex shape, or for a surface of the inside of a vacant space in a subject of treating having a minute vacant-space structure.
Up to now, as a method of surface treatment, surface treatment by plasma discharge has been known. Usually, the surface treatment by plasma discharge has been practiced in vacuum or in an environment of a reduced pressure; however, in recent years, it has become possible a treatment in an atmospheric pressure or in a pressure in the neighborhood of it.
For example, such a technology is disclosed in the publications of the examined patent applications H2-48626, H4-74372, H6-72308, and H7-48480, and in the publications of the unexamined patent applications H2-281734, H3-229886, H3-236475, etc.
Now, in one of the most orthodox conventional methods of treatment, a subject of treating is exposed to a gas, which is caused to have activated species by a discharge (hereinafter referred to as a discharge-activated gas for simplicity) in the inner part of the discharging space. In this case, this method does not cope with a surface treatment for a subject of treating positioned apart from the discharging space. Further, for example, if a subject of treating having minute vacant spaces itself is placed between the electrodes and treated, the outer surface of the subject can be treated but the inside of the minute vacant spaces can not be treated because nearly no plasma is generated there, or the efficiency of treatment has been extremely low and very long treatment time has been necessary (refer to FIG. 10).
On the other hand, in recent years, for a method of treating only a specified part of a subject of treating, a plasma treatment method of a blowing-out type, in which excited active species of the discharge-activated gas generated by a plasma discharge under an atmospheric pressure is blown to the desired treating area only, has been found out. For example, the publications of the unexamined patent applications H3-219082 (by Yukiko Okazaki et al.), H6-2149, H4-358076, H9-232293, H11-251304, H11-260597, H11-335868, etc. can be cited.
In such a conventional technology as described in the above, in a conventional atmospheric plasma of a blowing-out type, the contact of a subject of treating with the excited active species is dominated by the uncontrolled gas flow depending on the amount of flow of the gas, gas tubing path, etc.; therefore, there have been a problem in the case of a treatment at a low amount of gas flowing, a problem such that a treating part having a complex shape, a treating part positioned apart from the blowing-out opening, or a treating part with which no gas jet collides cannot be treated efficiently, or selectively, etc.
However, because a method of an atmospheric plasma of a blowing-out type is a method to practice a treatment by bringing excited active species (radicals, ions, etc.) generated in a plasma generating space into contact with a portion to be treated, the inactivation of the excited active species influences the effect of the treatment remarkably for the reason of its principle. That is, the larger the distance between the plasma generating space and the subject of treating is, the more remarkably the effect of reforming is reduced; further, in the case where the vacant-space structure is minute or complex, the excited active species become difficult to enter further inside, which causes the effect of reforming to be almost lost.
It is an object of this invention, to treat portions positioned apart from the blowing-out opening for a discharge-activated gas without producing unevenness in a surface treatment of a subject of treating using a discharge-activated gas. It is another object of this invention to make it possible to treat, for example, a subject of treating having a complex shape. Further objects of this invention are to improve the efficiency of treatment by a large margin, to make it possible to shorten the treatment time or to lower the discharge output, and further, to make it possible to lower the damage of the subject of treating by the treatment, and as the result, to make possible a remarkable improvement of productivity, to state it concretely, to make possible a high-speed treatment, cost reduction by energy saving and by making running cost lower, and a high-quality surface treatment. Further objects of this invention are to manufacture a head for use in an ink jet printer by using this method of surface treatment, and to provide a device of surface treatment for it.
Accordingly, to overcome the cited shortcomings, the abovementioned objects of the present invention can be attained by methods and apparatus for treating a surface of a subject described as follow.
(1) A method for treating a surface of a subject to be processed under a surface treatment with a discharge-activated gas, comprising the steps of: generating the discharge-activated gas under substantially an atmospheric pressure at a discharging section, which comprises a first electrode coated with a first dielectric substance; placing the surface of the subject between an outlet of the discharging section and a second electrode disposed at a position separating from the discharging section; and treating the surface of the subject with the discharge-activated gas flowing from the outlet of the discharging section.
(2) The method of item 1, wherein the second electrode is grounded.
(3) The method of item 1, wherein a second dielectric substance is either coated or placed on a surface of the second electrode.
(4) The method of item 1, wherein the surface of the subject is coated with a high polymer material.
(5) The method of item 1, wherein the second electrode is disposed at such a position that the subject contact the second electrode either directly or indirectly.
(6) The method of item 1, wherein the second electrode is disposed in such a direction that the discharge-activated gas flows after the surface of the subject is treated.
(7) The method of item 1, wherein an electronic potential gradient is created along a flowing direction of the discharge-activated gas.
(8) The method of item 1, wherein the discharging section further comprises a third electrode disposed opposite the first electrode.
(9) The method of item 1, wherein the discharge-activated gas includes either a helium gas or an argon gas.
(10) The method of item 1, wherein the generating step further comprises the steps of: introducing a dischargeable gas into a discharging space of the discharging section from an inlet located at a side of the discharging section; applying an electronic potential onto the first electrode so that the discharge-activated gas is generated by discharging actions performed in the discharging space filled with the dischargeable gas; and gushing the discharge-activated gas from the outlet located another side of the discharging section through the discharging space.
(11) The method of item 1, wherein the subject comprises at least two openings including a first opening and a second opening, and the discharging section is set at the first opening, while the second electrode is set at the second opening.
(12) The method of item 11, wherein an interior surface of the subject is processed under the surface treatment.
(13) The method of item 11, wherein the first opening is an intake section of the discharge-activated gas, and the second electrode is an exhaust section of the discharge-activated gas.
(14) The method of item 11, wherein the first electrode is disposed at such a position that the first electrode contacts at least a part of an outer surface of a dischargeable-gas intake tube.
(15) The method of item 12, wherein the subject is an ink-jetting head, and the interior surface is a surface of an ink-flowing path fabricated in the ink-jetting head.
(16) The method of item 15, wherein the ink-jetting head comprises a piezoelectric element.
(17) The method of item 15, wherein the interior surface of the subject is treated by the discharge-activated gas so as to make the interior surface hydrophilic.
(18) The method of item 8, wherein discharging actions is performed in a gap between the first electrode and the third electrode and a distance between them is not greater than 50 mm.
(19) The method of item 1, wherein the surface of the subject is treated by the discharge-activated gas so as to make the surface hydrophilic.
(20) The method of item 1, wherein the surface of the subject is treated by the discharge-activated gas so as to form a thin film layer on the surface.
(21) The method of item 1, wherein the surface of the subject is treated by the discharge-activated gas so as to make the surface hydrophobic.
(22) The method of item 1, wherein the surface of the subject is treated by the discharge-activated gas so as to make the surface coarse.
(23) An ink-jetting head employed for an ink-jet printer, comprising: a base body; and an ink-flowing path formed in the base body; wherein an interior surface of the ink-flowing path is treated so as to make the interior surface hydrophilic, according to a method for treating the interior surface with a discharge-activated gas, comprising the steps of: generating the discharge-activated gas under substantially an atmospheric pressure at a discharging section, which comprises a first electrode coated with a first dielectric substance; placing the interior surface between an outlet of the discharging section and a second electrode disposed at a position separating from the discharging section; and treating the interior surface with the discharge-activated gas flowing from the outlet of the discharging section.
(24) An apparatus for treating a surface of a subject to be processed under a surface treatment with a discharge-activated gas, comprising: a discharging section, having a first electrode coated with a first dielectric substance, to generate the discharge-activated gas; a second electrode, disposed at a position separating from the discharging section, to guide the discharge-activated gas along an electronic potential gradient created by the second electrode.